Process of producing caustic.



Patented June 24,1902.

H.K,MO0RE PROCESS OF PRODUCING CAUSTIO.

(Application filed. Apr. 30, 1900.)

(No Model.)

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UITED STATES PATENT OFFICE.

HUGH KELSEA MOORE, OF LYNN, MASSACHUSETTS, ASSIGNOR TO MOOREELECTROLYTIC COMPANY, OF PORTLAND, MAINE, AND BOSTON, MASSA- CHUSETTS, ACORPORATION OF MAINE.

PROCESS OF' PRODUCING cAusTlc.

SPECIFICATION formingpart of Letters Patent No. 703,289, dated June 24,1902.

Application filed April 30, 1900. Serial No. 14,787. (No specimens.)

.15 tact with an aqueous solution exterior to the cathode. In such cellsmore or less inconvenience has'been experienced by reason of the variousimpurities which are found in the commercial salts, such impuritiesconsisting 2o principally of the chlorids, chlorates, and

sulfates of magnesium and calcium, and to a lesser degree of ferrousoxid, silica, and vegetable matter. The foreign chlorids found in saltsto be treated are elect-rolyzed and are converted into hydrates uponreaching the cathode, being precipitated on the outer surface of thediaphragm and in the cathode. The presence of the precipitated calciumor magnesium hydrates or the chlorates, sulfates of magnesium, andcalcium clogs the diaphragm and cathode and prevents the freepercolation of the electrolyte, also increasing the electricalresistance of the cell. The precipitation of these foreign substancesupon the surface of the cathode greatly reduces the active face thereof,and the polarization which results is highly injurious to the successfuloperation of the cell. Again, the heat generated by the electrolyticaction 0 in the cell causes the drying of the hydrate upon the exteriorof the cathode, this being increased by the upward escape of theliberated hydrogen, which induces a flow of air in close proximity tothe cathode and a consequent evaporation of the liquid therein,

whereby the hydrate is carbonated and a comparatively thick crustthereof is formed on the cathode. This layer of carbonate graduallythickens in the direction of the diaphragm, being aided by theheat ofthe cell, which causes the drying of the aqueous hydrate until theoperation of the cell is so retarded that the diaphragm has to beremoved and the cathode freed from encrusted material.

I have discovered that the precipitation of the hydrate of the foreignsubstances, such as calcium or magnesium, can be prevented by excludingair from the cathode, and consequently preventing the evaporation of theliquid contained in the hydrate. I accom plish this by enveloping thecathode in a bath of the hydrogen which is given off thereat, so that itisimpossible for the air to reach the cathode and cause the evaporationof the liquids or the carbonating of the hydrates.

On the drawing is illustrated a cell with which my process may becarried out, there being shown in section a cell and an automaticdose'r. or feeding-tank. Said cell comprises a receptacle having abottom 1, end walls 2, and longitudinal sills or bars 3 3, connectingthe end walls at their upper ends. The top of the cell is closed by acover 4. The parts thus far described are preferably constructed ofslate or other material capable of resisting the attacks of the chlorinor the chlorinated liquid, and they are connected together in anysuitable way, the top being cemented in place. The provision of thelongitudinal bars 3 3 leaves open the lower portion of the sides of thecell, and to, close the same I employ a diaphragm 5, preferablyconsisting of a layer or layers of asbestos paper, through which theelectrolyte maypercolate in considerable quantities. Outside of thediaphragms and in contact therewith are placed the cathodes, eachcathode consisting of a layer 6 of wire-cloth and a perforated plate 7of iron or other suitable metallic substance. The diaphragms andcathodes are secured in place in any suitable way, and they confine thebody of the electrolyte within the recep-.

tacle, the latter constituting the anode-compartment. The wire-cloth andperforated metallic plate constitute a spongy cathode capable ofretaining by capillary attraction a considerable body of the solution ofhydrate and the undecomposed electrolyte which percolates through thediaphragm. It will be observed that the end walls taper from top tobottom, whereby the diaphragms are farthest apart at their upper endsand nearest together at their lower ends.

The anode consists of a plurality of oblong carbon plates 8, which arepassed through apertures in the cover l and have their faces confrontingthe diaphragms. The carbons rest in a longitudinal groove 1, formed inthe base-plate 1, and the minute spaces between the anodes and the wallsof the aperture in the cover 4 are filled with any suitable putty orcement. The sides or faces of the anode are parallel, whereby the spacebetween each anode-face and the adjacent diaphragm is substantiallyV-shaped.

Provision is made for the escape of chlorin by means ofa suitable duct.(Illustrated conventionally in dotted lines at 9.) The receptacle restsupon an inclined plate 11, with which the cathode is in electricalcontact, said plate and said anode being the terminals of an electricalcircuit, as usual.

Outside of the cathode is placed a casing 12, which is secured tightlyto the longitudinal bars 3 3 and the end Walls 2 2, so as to form acompartment 13, surrounding the cathodes. The lower end of the casing isseparated from the plate 11 by a passage-way 14:, for a purpose to bedescribed. 15 represents more or less conventionally a tank from whichthe brine flows to the cell through a pipe 16, whereby the same level ofliquid is maintained in the cell and in the tank. The brine flows froman initial receiving tank 17 through a pipe 17 and float-cock 18 to thetank 15. Said float-cock is secured upon a shaft 19, journaled inbrackets 20 onthe wall of the tank, said shaft being provided with anarm 21, through which an adjusting screw 22 passes, said screw beingrotatively connectedtothe bracket. Byturningthesaid screw said cock maybe swung upon the axis of the shaft to permit a variation of the heightof the liquid in the tank, as will be understood without furtherexplanation. By this mechanism it will be seen that the height or columnof liquid in the cell may be varied by degrees by merely turning thescrew 22.

The tank and the cell are filled with the brine to be electrolyzed andthe electrical current is passed through the cell.

Assuming for illustration that the electro- A lyte consists of apractically-saturated solution of sodium chlorid and water, thefollowing result will occur: The current of electricity flowing from theanode to the cathode electrolyzes the solution, said solutionpercolating through the diaphragm and coming into contact with thecathode. The ions are given off at their respective electrodes, chlorinbeing given off at the anode and the sodium liberated at the cathodebeing changed into hydrate by the water of the undecomposed solution,which has percolated through the roefese diaphragm. The hydrogen gaswhich is given off at the cathode outside of the diaphragm fills thecompartment 13, formed by the casing 12, and escapes into the atmospherethrough the passage-Way 14. As the solution of hydrate and undecomposedelectrolyte fills the pores of the spongy cathode to saturation itbegins to gravitate therethrough, the electrolytic action continuing andthe undecomposed solution in the cathode being electrolyzed until theresultant hydrate which flows from the cathode to the plate 12 containsa maximum percentage of caustic and a minimum percentage of sodiumchlorid. As the compartment 13 becomes filled with hydro gen it, beinglighter than air, fills the top of the compartment, and gradually, as itincreases in volume, drives out all the air through the passage-way 14until the cathode is nearly enveloped in a steamy cloud of the hydrogen.This prevents the access of air to the cathode, and thereby prevents theevaporation of the liquid contained in the cathode and incidentallyprevents the oxidation of the copper or iron forming the oathode. Themagnesium or calcium chlorid which is contained in the electrolyte isdecomposed and is converted into hydrate in the cathode; but inasmuch asthe cathode is enveloped in the steamy cloud of hydrogen and theevaporation of the liquid in the cathode is prevented the magnesium andcalcium is not precipitated, but flows in solution with the sodiumhydrate onto the plate 11. The presence of the casing 12 and theconfining of the hydrogen therein prevents the hydrogen from carryingwith it a quantity of caustic vapor, which is usually disseminatedthrough the room by the escaping hydrogen, such particles of causticvapor being condensed upon the interior of the casing and flowingtherefrom to the plate 11. As it is well known that the resistance ofthe electrolyte decreases with the rise in temperature thereof, theemployment of the casing prevents the cooling of the cell and aconsequent increase in the voltage necessary for the production of ahydrate.

Having thus explained the nature of the invention and described a way ofconstructing and using the same, although without attempting to setforth all of the forms in which it may be made or all of the modes ofits use, I declare that what I claim is- 1. The herein-described processof electrolyzing the chlorids chlorates or sulfates of alkali metalsconsisting in bringing an aqueous solution thereof into contact with oneface of a diaphragm of sulficient porosity to permit free flow of thesolution; passing an electric current through said solution anddiaphragm to an unsubmerged foraminous cathode in contact with the otherface of the diaphragm; thereby converting the metal into hydrate by thewater of the undecomposed percolated solution and confining theliberated hydrogen gas in contact with the outer face of the IIO cathodeand thereby excluding atmospheric air, whereby the cathion solutionflows by gravitation from said cathode without evaporation and withoutthe carbonating of the hydrate.

2. The herein-described process of electrolyzing the chlorids chloratesor sulfates of alkali metals consisting in bringing an aqueous solutionthereof into contact with one face of a diaphragm of sufficient porosityto permit free flow of the solution; passing an electric current throughsaid solution and diaphragm to an unsubmerged foraminous cathode incontact with the other face of said diaphragm, thereby converting themetal ion into hydrate by the water of the undecomposed percolatedsolution, and continuing the electrolysis of said undecomposed solutionin the pores of said cathode; and excluding atmospheric air from thecathode and the solution therein contained, to prevent the precipitationof foreign metals present in the form of chlorids, chlorates hydrates orsulfates in the said solution.

3. The herein-described process of electrolyzing the chlorids chloratesor sulfates of alkali metals consisting in bringing an aqueous solutionthereof into contact with one face of a porous diaphragm of sufficientporosity to permit free flow of the solution; passing an electriccurrent through said solution and diaphragm to an unsubmerged foraminouscathode in contact with the other face of said diaphragm, therebyconverting the metal ion into hydrate by the water of the undecomposedpercolated solution, and continuing the electrolysis of saidundecomposed solution in the pores of said cathode, and confining theliberated hydrogen in a steamy bath in contact with the cathode to theexclusion of atmospheric air, substantially as described.

at. The herein-described process of preventing the precipitation of thehydrates of foreign sulfates or chlorids chlorates, in the electrolysisof commercial salts, which consists in bringing a saline solutioncontaining said sulfates or chlorids into contact with a diaphragm ofsufficient porosity to permit free percolation of said solution, passingan electric current from an anode in said solution to an unsubmergedcathode outside said diaphragm and enveloping the cathode in-a confinedbath of gas and thereby preventing the evaporation of liquid containedon the cathode.

5. The herein-described process of preventing the carbonating of thehydrate resulting from the electrolysis of the chlorids chlorates orsulfates of alkali metals, which consists in bringing a saline solutioncontaining said sulfates or chloridsinto contact with a diaphragm ofsufficient porosity to permit free percolation of said solution, passingan electric current from an anode in said solution to an unsubmergedcathode outside said diaphragm and entirely excluding atmospheric airfrom contact with the said hydrate.

6. The herein-described process of preventing the carbonating of thehydrate resulting from the electrolysis of the chlorids chlorates orsulfates of alkali metals, which consists in bringing a saline solutioncontaining said sulfates or chlorids into contact with a diaphragm ofsufficient porosity to permit free percolation of said solution, passingan electric current from an anode in said solution to an unsubmergedcathode outside said diaphragm and enveloping the cathode containingsaid hydrate in a bath of hydrogen gas, and thereby preventing thecontact of atmospheric air therewith.

7. The herein-described process of preventing the precipitation of thehydrates of foreign sulfates chlorates and chlorids, in the electrolysisof commercial salts, which consists in bringing a saline solutioncontaining said sulfates or chlorids into contact with a diaphragm ofsufficient porosity to permit free percolation of said solution, passingan electric current from an anode in said solution to an unsubmergedcathode outside said diaphragm and enveloping the cathode in a bath ofthe hydrogen gas liberated at the cathode and thereby preventing theevaporation of liquid contained on or in the cathode.

In testimony whereof I have affixed my signature in presence of twowitnesses.

HUGH KELSEA MOORE.

WVitnesses:

O. E. MONROE, O. E. YOUNG.

